Issue #3511 - Rationalize temporary lifetimes.

Major changes:

- Define temporary scopes in a syntax-based way that basically defaults
  to the innermost statement or conditional block, except for in
  a `let` initializer, where we default to the innermost block. Rules
  are documented in the code, but not in the manual (yet).
  See new test run-pass/cleanup-value-scopes.rs for examples.
- Refactors Datum to better define cleanup roles.
- Refactor cleanup scopes to not be tied to basic blocks, permitting
  us to have a very large number of scopes (one per AST node).
- Introduce nascent documentation in trans/doc.rs covering datums and
  cleanup in a more comprehensive way.

Author: nikomatsakis

src/librustc/lib/llvm.rs

@@ -1698,6 +1698,7 @@ pub mod llvm {
 
         pub fn LLVMDICompositeTypeSetTypeArray(CompositeType: ValueRef, TypeArray: ValueRef);
         pub fn LLVMTypeToString(Type: TypeRef) -> *c_char;
+        pub fn LLVMValueToString(value_ref: ValueRef) -> *c_char;
 
         pub fn LLVMIsAArgument(value_ref: ValueRef) -> ValueRef;
 
@@ -1847,8 +1848,10 @@ impl TypeNames {
 
     pub fn val_to_str(&self, val: ValueRef) -> ~str {
         unsafe {
-            let ty = Type::from_ref(llvm::LLVMTypeOf(val));
-            self.type_to_str(ty)
+            let s = llvm::LLVMValueToString(val);
+            let ret = from_c_str(s);
+            free(s as *c_void);
+            ret
         }
     }
 }

src/librustc/middle/astencode.rs

@@ -12,13 +12,14 @@
 use c = metadata::common;
 use cstore = metadata::cstore;
 use driver::session::Session;
-use e = metadata::encoder;
 use metadata::decoder;
+use e = metadata::encoder;
+use middle::freevars::freevar_entry;
+use middle::region;
 use metadata::tydecode;
 use metadata::tydecode::{DefIdSource, NominalType, TypeWithId, TypeParameter,
                          RegionParameter};
 use metadata::tyencode;
-use middle::freevars::freevar_entry;
 use middle::typeck::{method_origin, method_map_entry};
 use middle::{ty, typeck, moves};
 use middle;
@@ -146,6 +147,7 @@ pub fn decode_inlined_item(cdata: @cstore::crate_metadata,
         debug!("< Decoded inlined fn: {}::{}",
                ast_map::path_to_str(path, token::get_ident_interner()),
                tcx.sess.str_of(ident));
+        region::resolve_inlined_item(tcx.sess, &tcx.region_maps, &ii);
         decode_side_tables(xcx, ast_doc);
         match ii {
           ast::IIItem(i) => {

src/librustc/middle/borrowck/gather_loans/lifetime.rs

@@ -220,7 +220,7 @@ impl<'a> GuaranteeLifetimeContext<'a> {
 
         // If inside of a match arm, expand the rooting to the entire
         // match. See the detailed discussion in `check()` above.
-        let mut root_scope = match discr_scope {
+        let root_scope = match discr_scope {
             None => root_scope,
             Some(id) => {
                 if self.bccx.is_subscope_of(root_scope, id) {
@@ -231,17 +231,6 @@ impl<'a> GuaranteeLifetimeContext<'a> {
             }
         };
 
-        // FIXME(#3511) grow to the nearest cleanup scope---this can
-        // cause observable errors if freezing!
-        if !self.bccx.tcx.region_maps.is_cleanup_scope(root_scope) {
-            debug!("{:?} is not a cleanup scope, adjusting", root_scope);
-
-            let cleanup_scope =
-                self.bccx.tcx.region_maps.cleanup_scope(root_scope);
-
-            root_scope = cleanup_scope;
-        }
-
         // Add a record of what is required
         let rm_key = root_map_key {id: cmt_deref.id, derefs: derefs};
         let root_info = RootInfo {scope: root_scope};
@@ -301,8 +290,8 @@ impl<'a> GuaranteeLifetimeContext<'a> {
         // See the SCOPE(LV) function in doc.rs
 
         match cmt.cat {
-            mc::cat_rvalue(cleanup_scope_id) => {
-                ty::ReScope(cleanup_scope_id)
+            mc::cat_rvalue(temp_scope) => {
+                temp_scope
             }
             mc::cat_copied_upvar(_) => {
                 ty::ReScope(self.item_scope_id)
@@ -313,7 +302,7 @@ impl<'a> GuaranteeLifetimeContext<'a> {
             mc::cat_local(local_id) |
             mc::cat_arg(local_id) |
             mc::cat_self(local_id) => {
-                self.bccx.tcx.region_maps.encl_region(local_id)
+                ty::ReScope(self.bccx.tcx.region_maps.var_scope(local_id))
             }
             mc::cat_deref(_, _, mc::unsafe_ptr(..)) => {
                 ty::ReStatic

src/librustc/middle/borrowck/gather_loans/mod.rs

@@ -662,8 +662,9 @@ impl<'a> GatherLoanCtxt<'a> {
         //! with immutable `&` pointers, because borrows of such pointers
         //! do not require restrictions and hence do not cause a loan.
 
-        let lexical_scope = self.bccx.tcx.region_maps.encl_scope(lp.node_id());
-        if self.bccx.tcx.region_maps.is_subscope_of(lexical_scope, loan_scope) {
+        let rm = &self.bccx.tcx.region_maps;
+        let lexical_scope = rm.var_scope(lp.node_id());
+        if rm.is_subscope_of(lexical_scope, loan_scope) {
             lexical_scope
         } else {
             assert!(self.bccx.tcx.region_maps.is_subscope_of(loan_scope, lexical_scope));
@@ -688,7 +689,7 @@ impl<'a> GatherLoanCtxt<'a> {
             let arg_cmt = mc_ctxt.cat_rvalue(
                 arg.id,
                 arg.pat.span,
-                body.id, // Arguments live only as long as the fn body.
+                ty::ReScope(body.id), // Args live only as long as the fn body.
                 arg_ty);
 
             self.gather_pat(arg_cmt, arg.pat, None);

src/librustc/middle/borrowck/move_data.rs

@@ -471,7 +471,7 @@ impl MoveData {
             for path in paths.get().iter() {
                 match *path.loan_path {
                     LpVar(id) => {
-                        let kill_id = tcx.region_maps.encl_scope(id);
+                        let kill_id = tcx.region_maps.var_scope(id);
                         let path = {
                             let path_map = self.path_map.borrow();
                             *path_map.get().get(&path.loan_path)
@@ -490,7 +490,7 @@ impl MoveData {
                     var_assignments.get().iter().enumerate() {
                 match *self.path_loan_path(assignment.path) {
                     LpVar(id) => {
-                        let kill_id = tcx.region_maps.encl_scope(id);
+                        let kill_id = tcx.region_maps.var_scope(id);
                         dfcx_assign.add_kill(kill_id, assignment_index);
                     }
                     LpExtend(..) => {

src/librustc/middle/mem_categorization.rs

@@ -60,7 +60,7 @@ use syntax::parse::token;
 
 #[deriving(Eq)]
 pub enum categorization {
-    cat_rvalue(ast::NodeId),           // temporary val, argument is its scope
+    cat_rvalue(ty::Region),            // temporary val, argument is its scope
     cat_static_item,
     cat_copied_upvar(CopiedUpvar),     // upvar copied into @fn or ~fn env
     cat_stack_upvar(cmt),              // by ref upvar from ||
@@ -585,21 +585,26 @@ impl mem_categorization_ctxt {
     pub fn cat_rvalue_node<N:ast_node>(&self,
                                        node: &N,
                                        expr_ty: ty::t) -> cmt {
-        self.cat_rvalue(node.id(),
-                        node.span(),
-                        self.tcx.region_maps.cleanup_scope(node.id()),
-                        expr_ty)
+        match self.tcx.region_maps.temporary_scope(node.id()) {
+            Some(scope) => {
+                self.cat_rvalue(node.id(), node.span(),
+                                ty::ReScope(scope), expr_ty)
+            }
+            None => {
+                self.cat_rvalue(node.id(), node.span(), ty::ReStatic, expr_ty)
+            }
+        }
     }
 
     pub fn cat_rvalue(&self,
                       cmt_id: ast::NodeId,
                       span: Span,
-                      cleanup_scope_id: ast::NodeId,
+                      temp_scope: ty::Region,
                       expr_ty: ty::t) -> cmt {
         @cmt_ {
             id:cmt_id,
             span:span,
-            cat:cat_rvalue(cleanup_scope_id),
+            cat:cat_rvalue(temp_scope),
             mutbl:McDeclared,
             ty:expr_ty
         }

src/librustc/middle/pat_util.rs

@@ -108,3 +108,14 @@ pub fn pat_contains_bindings(dm: resolve::DefMap, pat: &Pat) -> bool {
     });
     contains_bindings
 }
+
+pub fn simple_identifier<'a>(pat: &'a Pat) -> Option<&'a Path> {
+    match pat.node {
+        PatIdent(BindByValue(_), ref path, None) => {
+            Some(path)
+        }
+        _ => {
+            None
+        }
+    }
+}